1. Field of the Invention
This invention relates to an injecting unit provided with a locking apparatus for a program-controlled simultaneous locking of a plasticizing cylinder to a carrying block and for simultaneously locking a feed screw to a screw-driving shaft. Said feed screw comprises a profiled coupling portion, which is adapted to be coupled to a coupling section of the screw-driving shaft. The feed screw is axially displaceable by hydraulic injecting cylinders for effecting an injection of plastic sliders, which are disposed on opposite sides of the axis of the plasticizing cylinder and are radially guided on the carrying block and by means of at least one hydraulic unlocking cylinder are adapted to be radially displaced from a locking position to an unlocking position. A screw-locking slider is radially guided on and non-rotatably connected to the coupling section and is adapted to assume a desired angular position, in which the screw-locking slider is adapted to lock the feed screw to the screw-driving shaft and in said desired angular position is adapted to be displaced by said unlocking cylinder from a locking position to an unlocking position, which desired angular position is adapted to be determined by means of a position control device for arresting the screw-driving motor.
The "desired angular position" is that angular position in which the feed screw is to be arrested and in which the feed screw can be locked to the screw-driving shaft in the course of a program-controlled exchange of a plasticizing unit which comprises the plasticizing cylinder and the feed screw.
2. Description of the Prior Art
An injecting unit of the kind described first hereinbefore is disclosed in U.S. Pat. No. 4,704,078. In that injecting unit the hydraulic unlocking cylinder for controlling the cylinder-locking sliders and the screw-locking sliders acts through at least one spreading wedge onto two screw-locking sliders, which are disposed on opposite sides of the axis of the feed screw. For an unlocking movement the spreading wedge moves in between the two screw-locking sliders and moves the same out of their locking position in tracks at right angles to the axis of the hydraulic unlocking cylinder. That design requires relatively expensive tracks in a separate housing for the screw-locking sliders.